This invention relates to a mobile communication unit and, more particularly, to an apparatus and method for conveniently placing a call to a telephone number which is not found among a list of frequently called telephone numbers stored in a database within the mobile communication unit.
Mobile communication units, such as cellular telephones, often have features allowing a user to store the names and telephone numbers of parties frequently called by the user in a phonebook-type database within the mobile communication unit. Such a database typically includes a number of data records, each containing the name and telephone number of a party frequently called by the user and a unique searchable index item in a form representing an alpha character string. The name of the party is often used as the index item.
To retrieve a phone number from such a database, the user presses the keys on the telephone keyboard to indicate a desired character string. Circuitry and software within the mobile communication unit compare the desired character string, starting with the first character entered and proceeding to the last character entered, with the same position characters of index items in the data records stored in the database. Data records having index items matching the desired character string are selected from the database within the mobile communication unit and, typically, a grouping of names, telephone numbers, or another portion of the data records containing at least a partial match with the desired character string are displayed on a display device of the mobile communication unit. The mobile communication unit also typically includes a scrolling and selecting device for scrolling through the displayed portions of the data records and selecting a name or telephone number that the user desires to call.
If mobile communication units were equipped with full alpha-numeric keyboards of the type found on a typewriter or a personal computer, the process described above could be accomplished in a relatively straightforward manner. Mobile communications units are generally far too small, however, to include a full alpha-numeric keyboard. More typically, the mobile communication unit will have a standard telephone keypad wherein each of the keys from 2-6 and the 8 key also represent three alpha characters, and the 7 and 9 keys also represent four alpha characters each. Because each of the keys can potentially represent a number and three or four alpha characters, the keystrokes representing the desired character string can represent a large number of potential alpha-numeric combinations. The circuitry and software within the mobile communication unit must, therefore, have the ability to resolve the ambiguity created by the large number of potential combinations represented by the keystrokes of the desired character string.
In the past, statistical analysis, and sequential matching, keystroke by keystroke, of the desired character string with index items in the database potentially matching the character string have been utilized for performing a search of the database and resolving the ambiguity of the input. Because it is typically much easier for a user to remember the name of a party he desires to call, rather than the phone number of that party, these prior systems generally assume that the character string is an alpha representation of an index item such as the name of the party. Examples of circuitry and software of this type are provided by U.S. Pat. No. 5,953,541 to King et al; U.S. Pat. No. 5,337,347 to Halstead-Nussloch; U.K. Patent Appln. No. 9804831.7 to Gang Hu, and Chang; and U.S. Pat. No. 6,061,437 to Yoon.
A common problem with all prior techniques, however, is that when they recognize that there is no entry in their database that could possibly match the desired character string, the search routine abruptly terminates, at best, with a message notifying the user to switch the phone to a normal dial-by-phone-number mode. Switching the phone to a normal dial-by telephone number mode typically involves pressing additional function keys to switch modes. The character string inputted up to the time the search routine was terminated is lost and must be re-entered after the mode of operation is switched.
Further improvement is needed to make such systems truly user-friendly for users of mobile communication units.